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A gyroscope is a rigid circular or spherical mass rotating around an axis and for over 100 years motorcycles have come with three of them: a front wheel, a rear wheel and a crank (if you're being pedantic you could include cams, balancer shafts, gearbox, clutch etc).
The classic mechanical model of a gyroscope ranges from the very small – electrons spinning around an atom's nucleus – to the very large – the Earth.

Most of us have an innate feel for balancing a high centre of gravity on a relatively short wheelbase. Say, like a motorbike. Its centre of gravity is the point at which the sum of the surrounding mass is zero, and is largely determined by the location of the engine, the heaviest part of the package. Usually the CoG is midway between the wheels (half the wheelbase) and 60 to 75cm off the ground; just above the engine, in front of your knees.
Or at least it is until you get on.

Anyone with fingers knows bikes vibrate, sometimes strongly enough to make picking your nose impossible. But how we perceive vibration depends on its type, pattern, frequency and cause.
Bikes are subject to different types of vibration. A bumpy road creates random forced vibration at medium to high frequency (around 5-35 Hz depending on vehicle speed). It's perceived as unpleasant, as is head buffeting caused by wind turbulence. Engineers and aerodynamicists try to minimise these bad vibrations.
But we usually talk about engine vibration. There are many sources...

From the launch of Yamaha's new Super Ténéré: "The exhaust pipe connection between the two headers is discontinued to give more character to the engine. The link pipe gives a flat feeling to the curve, so removing it makes the engine a bit more peaky."
This is all about exhaust gas. When a four-stroke is tuned for power it means more revs, and so the cylinders have thousandths of second to fill with fresh mixture, compress it, burn it and pump it out again. To get enough mixture in and out, inlet valves open early and exhaust valves stay open for longer – so both are open at the same time.

Twenty one years ago BMW launched the R1100RS with a Telelever front end. It's gone on to be fitted to the most popular bike of the 21st Century, BMW's GS. Yet still – apart from BMW's other forkless system, Duolever – conventional telescopic forks survive on all other bikes, including MotoGP. Why?

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